1. Field of the Invention
The present invention relates to a disk drive, and, more particularly, to a disk drive that reduces vibration and noise generated during rotation of a disk.
2. Description of the Related Art
In general, disk drives record information on a recording surface, including concentric tracks of a disk, or read information from the recording surface. That is, data are recorded on the recording surface of a disk rotating with a linear velocity or read out from the recording surface, by emitting a laser beam from an optical pickup device sliding in a radial direction with respect to the disk.
FIG. 1 is a perspective view illustrating a conventional disk drive. Referring to FIG. 1, a conventional disk drive typically includes a disk tray 10 on which a disk 60 is loaded, a disk driving portion 20 rotating the disk 60, a disk chucking apparatus 30 having a chuck plate 31 and a disk chuck, an optical pickup device 40 performing data recording/reproduction and an optical pickup device driving portion 50. The disk tray 10 has a window 11 penetrating the disk tray 10 to facilitate operation of the disk chucking apparatus 30 and the optical pickup device 40.
To accurately read data recorded on a recording surface of the disk 60 or record data on the disk 60, a beam emitted from the optical pickup device 40 must be accurately incident on a track of the recording surface of the disk 60. Also, the optical axis of the beam emitted from the optical pickup device 40 must be maintained at a predetermined angle with respect to the recording surface of the disk 60. However, when vibration is generated by the rotating disk 60, recording and reproduction performance of the disk drive are deteriorated. Furthermore, as the speed of disk drives increases, the vibration generated during the rotation of the disk 60 has a considerable affect on reliability in data recording and reproduction. Also, noise generated during use of most office machines directly affects the office environment and work efficiency. Thus, removing or reducing the noise and vibration is very important.
The noise and vibration occurring during the rotation of the disk 60 are generated by friction between the surface of the rotating disk 60 and surrounding air; a difference in pressure around the disk 60; collision of air occurring between the rotating disk 60, the disk tray 10, and an inner surface of the disk drive, and perturbation generated according to the air collision ; and turbulence formed around the disk 60.
Conventional technologies to reduce noise and vibration generated in the disk drive have been developed. First, Korean Patent Publication No. 2000-75152 discloses a noise and vibration reduction technology to reduce the transmission of sound waves by filling gaps between constituent elements in the disk drive through which noise is discharged with a sound insulating material or a sound absorbing material, or using a muffler effect technology of a vehicle by forming a plurality of grooves at predetermined intervals along the outer circumference of a portion of a chuck plate of a disk chucking apparatus corresponding to an outer circumference of a disk.
Korean Patent Publication No. 2001-16753 discloses a technology of reducing noise and vibration that uses an auto-balancing mechanism in which balls are inserted in a plurality of races provided in a turntable of a disk. The balls move in a radial direction to compensate for the eccentricity of the turntable
Korean Patent Publication No.1999-80545 discloses a noise reduction apparatus for reducing noise and vibration due to high speed turbulence flow by installing a plurality of blades on an upper surface of a disk tray that are separated at predetermined intervals, or forming a screw-type or vortex-type groove or dimple to reduce air resistance due to the shape of the profile of the disk, air friction on the upper and lower surfaces of the disk, collision with a wall surface due to a separation phenomenon at a leading end of the disk, and noise due to high speed turbulence flow during rotation of the disk. Thus, air resistance on the disk during rotation of the disk is reduced, a gradient in the speed of the air flow in a boundary layer of the upper and lower surfaces of the disk is removed, and collision of high speed air flow at the leading end of the disk is prevented.
FIG. 2 is a view depicting the flow of air above the upper surface of a rotating disk. Referring to FIG. 2, rotational turbulence 80 generated during rotation of the disk 60 rotates in the same direction as the rotation direction of the disk 60 between the upper surface of the disk 60 and a cover 70 of the disk drive. That is, when the disk 60 rotates clockwise, the rotational turbulence 80 rotates clockwise as well. The rotation speed of the rotational turbulence 80 is about 0.5 times the disk rotation speed. The speed of the rotational turbulence 80 is distributed such that a boundary layer (not shown) forms near the rotating disk 60 and also near an upper cover plate (not shown) of the disk drive. A free flowing layer of air forms between the two boundary layers.
The rotational turbulence 80 collides with surrounding structures such as the window portion 11 formed in the disk tray 10, the optical pickup device 40, and a gear portion (not shown) disposed under the disk tray 10, to generate a perturbation component. In particular, a strong rotational turbulence is formed in the free flow layer, which generates vibration and noise by colliding with or causing friction with the structures.
Thus, it is important to reduce noise and vibration generated by the disk rotation by weakening or removing the turbulence by removing the perturbation component. Also, even when the chuck plate 31 is provided, perturbation is generated due to the collision of air flow in the front side portion of the disk drive and, accordingly, flow noise is generated and transmitted outside the front side portion of the disk drive. Because the rear side portion of the disk drive is within the main body of a computer, noise generated here may not be a problem. However, the noise transmitted outside the front side portion of the disk drive is very important. Therefore, an appropriate solution to control this problem is needed.